Flexible polyurethane foam is commonly produced by methods of molding and free-rise. The process of molding polyurethane flexible foam involves introducing chemicals required for making foam, such as one or more polyols, one or more isocyanates and one or more additives, in the desired ratio by injection or open pour into an individual, multiple or continuous mold and allowing the reacting foam system to fill the mold(s).
Molded flexible polyurethane foam articles such as pillows, automotive seating, or head rests are made in various molds that have a mold release applied to the inside surfaces of the mold prior to injecting or pouring foam-forming chemicals into the mold. The mold release mixtures are typically sprayed to promote even coverage. However, there are other methods of application such as wiping, pouring, and any other method which deposits a thin film or a film thick enough to provide the desired mold release properties on a surface.
A mold can be defined as a hollow form or matrix that gives a particular shape to an article in a molten or plastic state. It can be constructed from a metallic or nonmetallic material and its shape can be simple or complex, depending on the nature of the molded part. Before the mold is used, it may be necessary to pretreat the mold surface, thereby improving the adhesion of the mold release mixture. This can be accomplished through various means such as sandblasting or disc sanding, sand paper polishing, degreasing, or electropolishing.
Conventional mold release compositions comprise materials such as waxes or silicones, which are dissolved or dispersed in a solvent carrier, which may be organic solvent-based, petroleum-based or water-based. Petroleum-based mold release compositions usually have a problem with imparting an odor to the foam surface. In order to remove petroleum or solvent odors from a molded foam part, it needs to be exposed to sufficient airflow to allow the odorous solvent(s) to volatilize or diffuse away from the foam surface prior to packaging. Water-based mold release compositions typically do not have the odor problems that solvent-based mold release compositions have.
Molded foams may have a problem with skin delamination, wherein the skin splits from the main body of the foam, if the mold is opened before the skin has sufficiently cured. In order to reduce skin delamination, the foamed part may have to stay in the mold for a longer time and at a higher temperature to crosslink or cure the skin. Improving skin quality can increase de-molding time, thus reducing production output.
It is helpful and desirable to develop new, alternative and/or improved mold release mixtures to improve surface cure, create higher skin porosity, prevent skin delamination, and reduce de-molding times for the facilitation of higher production rates on mold lines.